concepts · 10
- 01
Copies You Can Trust
What congruent means, how to test it by turning and flipping, and which measurements you need to copy a shape.
- 02
Three Sides Are Enough
Why three side lengths fix a triangle completely: the SSS rule.
- 03
Naming Congruent Triangles
Why the order of letters in a congruence statement matters, and how to write one correctly.
- 04
Two Sides And The Angle Between
Equal angles only fix the shape. Two sides and the angle between them fix the whole triangle: the SAS rule.
- 05
Why SSA Is Not Enough
Build two different triangles from the same side-side-angle measurements, and see why SSA can't be trusted.
- 06
Two Angles And One Side
Two angles and the side between them (ASA), and how the 180° angle sum turns other cases into ASA (AAS).
- 07
Right Triangles And RHS
The one case where two sides and a non-included angle do work, right triangles (RHS), and all five rules together.
- 08
Angles Of Isosceles And Equilateral Triangles
Use congruence to prove that angles opposite equal sides are equal, and that each angle of an equilateral triangle is 60°.
- 09
Choosing The Right Congruence Test
Look at the measurements given, and decide which rule applies, or that none does.
- 10
Review: Geometric Twins
All five congruence rules, the two cases that fail, and the isosceles results, on the chapter's hardest questions.
